title: Hemodynamic adjustments during breath-holding in trained divers.
abstract: OBJECTIVE
  Voluntary breath-holding (BH) elicits several hemodynamic changes, but little is known about maximal static immersed-body BH. We hypothesized that the diving reflex would be strengthened with body immersion and would spare more oxygen than maximal dry static BH, resulting in a longer BH duration.
  
  
  METHODS
  Eleven trained breath-hold divers (BHDs) performed a maximal dry-body BH and a maximal immersed-body BH. Cardiac output (CO), stroke volume (SV), heart rate (HR), left ventricular end-diastolic volume (LVEDV), contractility index (CTI), and ventricular ejection time (VET) were continuously recorded by bio-impedancemetry (PhysioFlow PF-05). Arterial oxygen saturation (SaO2) was assessed with a finger probe oximeter.
  
  
  RESULTS
  In both conditions, BHDs presented a bi-phasic kinetic for CO and a tri-phasic kinetic for SV and HR. In the first phase of immersed-body BH and dry-body BH, results (mean ± SD) expressed as percentage changes from starting values showed decreased CO (55.9 ± 10.4 vs. 39.3 ± 16.8 %, respectively; p < 0.01 between conditions), due to drops in both SV (24.9 ± 16.2 vs. 9.0 ± 8.5 %, respectively; p < 0.05 between conditions) and HR (39.7 ± 16.7 vs. 33.6 ± 17.0 %, respectively; p < 0.01 between conditions). The second phase was marked by an overall stabilization of hemodynamic variables. In the third one, CO kept stabilizing due to increased SV (17.0 ± 20.2 vs. 10.9 ± 13.8 %, respectively; p < 0.05 between conditions) associated with a second HR drop (14.0 ± 10.0 vs. 12.7 ± 8.9 %, respectively; p < 0.01 between conditions).
  
  
  CONCLUSIONS
  This study highlights similar time-course patterns for cardiodynamic variables during dry-body and immersed-body BH, although the phenomenon was more pronounced in the latter condition.
authors.affiliation: CETAPS, EA No. 3832, Faculté des Sciences du Sport, Boulevard Siegfried, Université de Rouen, 76130, Mont-Saint-Aignan, France, guillaume.costalat1@univ-rouen.fr.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Costalat
authors.forename: Jeremy
authors.initials: J
authors.lastname: Coquart
authors.forename: Ingrid
authors.initials: I
authors.lastname: Castres
authors.forename: Claire
authors.initials: C
authors.lastname: Tourny
authors.forename: Frederic
authors.initials: F
authors.lastname: Lemaitre
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D062485:Breath Holding; D004242:Diving / Q000502:physiology*; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D012018:Reflex